Trehalose mobilization during early germination ofPilobolus longipes sporangiospores

Pilobolus longipes spores were activated by either exogenous glucose or 6-deoxyglucose. Trehalose content of glucose-activated spores increased and the substrate for trehalose synthesis was exogenous glucose. Addition of 6-deoxyglucose resulted in mobilization of trehalose, with about 20% of the reserve being consumed in the first hour. Little or no change in trehalase activity occurred during spore activation. Most of the trehalase activity associated with spores could be removed by washing with phosphate buffer. This extracellular enzyme was relatively stable, had a pH optimum of 5.6 and a K_m of about 0.5 mM and was estimated to be 66,000 in molecular weight. The specific activity of the crude enzyme extracts fromP. longipes was not influenced by cAMP, but, under the same conditions, the regulatory trehalase fromSaccharomyces cerevisiae became activated. These experiments indicate that trehalase activity in germinatingP. longipes spores may not be regulated by cAMP-dependent phosphorylation. Instead, the results suggest that trehalose is mobilized by a decompartmentation process.